Williams Syndrome (WS) is a complex neurodevelopmental disorder involving mild to moderate mental retardation, an unusual personality profile, infantile hypercalcemia, dysmorphic facial features, and supravalvar aortic stenosis (SVAS). WS is a contiguous gene disorder resulting from submicroscopic deletions of chromosome 7q11.23. The goal of the proposed study is to create a medical and behavioral profile of WS ("a quantifiable assay of the WS behavioral profile") and to use this profile to identify specific genes underlying behavioral features of WS and carryout genotype-phenotype correlation studies. The specific aims include ascertainment and characterization of individuals who have features that overlap with WS; 2) identification and characterization of the cardinal features of the phenotype of WS and phenotypes of individuals with smaller WS deletions; 3) identification of genes responsible for specific phenotypic features of WS through deliniation of a refined physical map of the WS region, cloning and characterization of genomic DNA within this region, and identification of new genes in the region. An initial specific goal is to identify genes responsible for the personality characteristics of WS as well as other specific phenotype features.